Electrically operated valves, such as fuel injectors for injecting liquid fuel into an internal combustion engine, spray and atomize fuel. The fuel injector, then, is a solenoid through which fuel is metered. Typically, a solenoid valve comprises an armature movable between a first and second position. The extremes of these first and second positions are often defined by mechanical stops. Armatures can be moved in one direction by an electro-magnetic force generated by a coil of wire and moved in the opposite direction by a return spring. When the armature impacts a stop, it bounces. Each bounce of the armature, or valving element, meters a small uncontrolled amount of fuel into the engine, to the detriment of emissions.
Electromagnetic solenoids require certain times to initiate motion during energization and de-energization. When electric current is applied to the injector coil, a magnetic field is created. This causes the armature to move upward, allowing fuel, under pressure, to flow out of the injector nozzle. When the injector is de-energized, the flow of fuel is halted.
Piezoelectric actuators have been tried for fuel injectors in the past, but have proved impractical because displacement of the actuator is too small. Various mechanical motion amplifiers have proved impractical, also because displacement of the actuator is too small.
It is seen then that it would be desirable to have a solenoid motion initiator capable of providing the necessary displacement as well as the necessary speed for improved linear flow range.